<?php 
/*
$num = 1.1;
//向上取整
//echo ceil($num);
//向下取整
//echo floor($num);
*/


/*
$arr = array(1,100,200,5);
//获得最大值
echo max($arr);
*/

/*
$arr = array(1,100,200,5);
//获得最小值
echo min($arr);
*/

/*
$num = 2.5;
//四舍五入
echo round($num);
*/

//0-3的随机数，包含0和3
//echo mt_rand(0, 3);

//指数表达式 2的3次方 2*2*2
//echo pow(2, 3);






















?>
<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8" />
	<title>Document</title>
	<!--随机变换背景色-->
	<link rel="stylesheet" type="text/css" href="css/<?php echo mt_rand(1, 3) ?>.css"/>
</head>
<body>
	
</body>
</html>